The present invention relates to water treating devices and, more particularly, to a control arrangement for controlling the regeneration of a water softener system.
Water softener systems of the type with which the present invention is used have a treatment tank filled with a resin material, such as zeolite. Hard water is passed through the zeolite bed and an ion exchange process takes place in which the sodium ions are exchanged for the hard metal ions in the water. The water treating efficacy of the zeolite bed will be gradually reduced and, after a predetermined quantity of water has been treated, the zeolite bed will be depleted. The zeolite bed may be regenerated, however, by passing a salt brine solution through it such that the ion exchange process is reversed. The maximum length of time between successive regeneration processes is dependent both upon the hardness of the water and upon the quantity of water which is treated.
Prior art regeneration devices have generally been controlled by simple timer arrangements in which a regeneration cycle is initiated, usually late at night, every several days. Such a regeneration control results, at best, in regeneration at times which roughly approximate those at which regeneration is actually needed. During periods of unusually high water usage, the zeolite bed may be depleted substantially before regeneration occurs, thus resulting in only partially treated water being supplied by the softener. Conversely, during periods of time in which little water is used, regeneration will occur too frequently and brine solution will be wasted.
Several prior art devices have been designed to minimize the waste of brine solution while providing more frequent regeneration during periods of heavy water use. One such device is shown in U.S. Pat. No. 3,176,844, issued Apr. 6, 1965, to Nelson in which the resistance between electrodes in the softener tank is measured to determine when the softening capability of the zeolite bed is depleted, and thereafter to initiate the regeneration operation. Although temperature compensation is provided in the Nelson device, the resistivity of the zeolite bed is not directly proportional to its softening capability and some errors may result.
Another approach taken to minimize the amount of brine solution required for regeneration is shown in U.S. Pat. No. 3,687,289, issued Oct. 29, 1972, to Tischler. In the Tischler device, a predetermined portion of the treated water is metered to a chamber having an adjustable water storage capacity. The water stored in the chamber is periodically directed to the brine storage tank. When the liquid level in the brine tank reaches a predetermined height, a timer is actuated resulting in regeneration of the system at a selected time during the following 24 hour time period. Although a definite improvement over the prior art, the Tischler device requires substantial hardware and initiates regeneration only at the predetermined time specified by the timer. The brine level chosen for actuation of the timer could be set such that the softener will be capable of thereafter treating a normal 24 hour supply of water. If, however, an unusually large quantity of water were treated, it is quite possible that the softening capability of the system would be depleted prior to initiation of the regeneration process.
Accordingly, it is seen that there is a need for a simple but accurate regeneration control which will monitor the quantity of water treated and initiate regeneration at a selected time when less than a day's capacity of softening remains or, alternatively, when the softening capacity of the system is completely depleted, which ever occurs first.